A 3,500-sq.-ft. Walmart? Sounds hard to believe, but the world’s largest retailer broke new ground in January when it opened “Walmart on Campus” on the grounds of the University of Arkansas in Fayetteville. The store, open to students and non-students alike, reflects the sea change that has occurred at Wal-Mart Stores and throughout the industry during the past couple of years as retailers across the board show increased flexibility and a willingness to rethink formats and footprints — most often, by thinking smaller.